One factor in determining whether or not to exploit an offshore oil and gas field is the feasibility of handling and transporting the hydrocarbons to market once they are produced. Generally, hydrocarbons produced offshore must be transported to land-based facilities for subsequent processing and distribution. Temporary storage may be provided at the offshore production site for holding limited quantities of hydrocarbons produced and awaiting transport to shore. In some cases, equipment is also provided at the offshore production site for separating and/or treating the produced hydrocarbons prior to storing and transporting them to shore.
In the case of an offshore production facility located relatively close to shore, hydrocarbons produced may be feasibly transported to shore through a pipeline system extending from the offshore site (e.g., offshore platform or subsea wells) to the shore along the ocean floor or seabed. This type of pipeline system is advantageous, when feasible, because it permits the constant flow of hydrocarbons to shore regardless of the weather or other adverse conditions. However, in some parts of the world, the use of a seabed pipeline system for transporting hydrocarbons to shore may be cost-prohibitive and/or impractical.
For offshore facilities located a great distance from shore, construction of a pipeline to shore is typically not practicable. In these cases, storage (and possibly production) vessels are used to store the hydrocarbons. The hydrocarbons are transported to shore by a shuttle tanker that is configured to receive the hydrocarbons from the storage vessel during an offload operation.
Because the storage vessel and the shuttle tanker both float on the water surface, their operations are largely dependent upon surface conditions, such as wind, wave, and current conditions. An offload operation that requires connection of an offload hose between the vessels is a complex operation in even benign conditions. As the conditions become more extreme, such an operation increases in complexity to the point that operations during severe or unfavorable conditions are often postponed, thereby leading to lost opportunity due to the downtime.
Current industry off-take solutions force tankers offloading from FPSO's to accept 100% of the movement about the FPSO, thereby limiting the operability window uptime. The current solutions in the market space include non-DP tankers with a Hawser connection to an FPSO, a DP tanker/Hawser combination connection to a FPSO, and a DP tanker to FPSO connection via only hoses. In all current industry solutions, the tanker systems are the sole solution for vessel control and off take acceptance.